The Calera process for the capture and conversion of CO2 takes its lead from nature. The earth’s atmosphere has seen even higher concentrations of CO2 in the past and nature has dealt with these high levels of CO2 by a mineralization process whereby marine organisms use CO2 to form calcium carbonate structures that overtime become deposited on the ocean floors. It is estimated that up to 100 million billion tonnes of CO2 have been stored in the geological record in the form of calcium carbonate.
CO2 Capture and Use — Inspired by Nature
The special form of calcium carbonate that Calera makes in its process also mimics or copies the form of calcium carbonate that marine organisms use to make their shells and other structures. The special form of calcium carbonate is a cement or binder in that when water and proprietary additives are used, the cement from the Calera process binds together and creates structures with high strength and toughness that are used to make a range of building materials.
Calcium carbonate is known to exist in nature in different forms know as polymorphs. The Calera process results in the production of the vaterite polymorph which when stored in the absence of water is stable. When water and other proprietary additives are added to the vaterite polymorph, a cement reaction occurs in which the vaterite transforms via a dissolution and reprecipitation reaction to form another polymorph of calcium carbonate known as aragonite. It is this conversion of vaterite to aragonite that results in a material with high strength, just as natural systems, such as nacre (mother of pearl) are also constructed from the aragonite polymorph of calcium carbonate.